The Anne Arundel County branch of the NAACP is seeking a federal Justice Department probe of the county's Police Department, claiming that there is a lack of diversity in the department and not enough promotion opportunities for black officers.

Jacqueline Allsup, president of the county branch of the National Association for the Advancement of Colored People, said she sent a letter Monday to Sen. Barbara A. Mikulski, asking her to make a formal request for a Justice Department investigation. Efforts by the officers to address their complaints within the department have not yielded results, Allsup said.

Sgt. Eric Scott, a 20-year veteran of the department who turned to the NAACP, said that African-American officers are subjected to disparate treatment and given fewer opportunities to join specialized units — including the Criminal Investigations Division and the Special Enforcement Section — with the exception of the School Resource Unit, he said. Scott also complained that the department has failed to recruit enough African-American officers to deal with an increasingly diverse population.

"I would hope our department does the right thing. I would hate to think it would take an outside agency to see that it happens," he said.

In an emailed statement, the Police Department said it does not tolerate discrimination and is committed to diversity. A spokesman did not address some of the specific claims made by the NAACP and Scott.

"The Anne Arundel County Police Department has an excellent working relationship with the NAACP and the Human Relations Commission," spokesman Justin Mulcahy wrote. "The agency remains committed to supporting minority recruiting, in part with the assistance of our minority recruiter, and creating a diverse and positive work environment for all employees."

Of 635 county police officers, 47 are black, according to the department.